A connecting rod assembly is provided for varying a compression ratio of an internal combustion engine having a crankshaft and a piston. The assembly includes a first portion adapted to be connected to the crankshaft and having a cylindrical aperture. The assembly further includes a second portion adapted to be connected to the piston and movable with respect to the first portion. In addition, the assembly includes a locking element having a cylindrical portion that is disposed at least partially in the cylindrical aperture. The locking element is movable between an unlocked position and a locked position for locking the second portion at a first position relative to the first portion, wherein the first position corresponds to a first compression ratio of the engine.
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14. A variable compression engine comprising:
a crankshaft; a reciprocating piston; a connecting rod assembly including a first portion connected to the crankshaft and having a cylindrical aperture, a second portion connected to the piston and movable with respect to the first portion, and a locking element having a cylindrical portion that is disposed at least partially in the cylindrical aperture, the locking element being movable between an unlocked position and a locked position for locking the second portion at a first position relative to the first portion, the first position corresponding to a first compression ratio of the engine.
1. A connecting rod assembly for varying a compression ratio of an internal combustion engine, the engine having a crankshaft and a piston, the connecting rod comprising:
a first portion adapted to be connected to the crankshaft and having a cylindrical aperture; a second portion adapted to be connected to the piston and movable with respect to the first portion; and a locking element having a cylindrical portion that is disposed at least partially in the cylindrical aperture, the locking element being movable between an unlocked position and a locked position for locking the second portion at a first position relative to the first portion, the first position corresponding to a first compression ratio of the engine.
13. A connecting rod assembly for varying a compression ratio of an internal combustion engine, the engine including a cylinder, a reciprocating piston disposed within the cylinder, and a crankshaft having a crankpin, the connecting rod comprising:
a bearing retainer adapted to be connected to the crankpin and having first and second ends, the bearing retainer further having a first cylindrical bore and a first slot disposed proximate the first end, and a second cylindrical bore and a second slot disposed proximate the second end; a body portion adapted to be connected to the piston, the body portion having a longitudinal body portion axis and being axially movable with respect to the bearing retainer to effect a selective displacement of the body portion relative to the bearing retainer, the displacement causing a change in the effective length of the body portion and the compression ratio of the engine; a first locking mechanism including a first locking element that is movable between an unlocked position and a locked position, the first locking element having a first cylindrical portion and a first projection extending from the first cylindrical portion, the first cylindrical portion being disposed in the first cylindrical bore and having a first aperture, and the first projection extending through the first slot, the first locking mechanism further including a first spring disposed at least partially in the first aperture and engaged with the first locking element for urging the first locking element toward the locked position; and a second locking mechanism including a second locking element that is movable between an unlocked position and a locked position, the second locking element having a second cylindrical portion and a second projection extending from the second cylindrical portion, the second cylindrical portion being disposed in the second cylindrical bore and having a second aperture, and the second projection extending through the second slot, the second locking mechanism further including a second spring disposed at least partially in the second aperture and engaged with the second locking element for urging the second locking element toward the locked position; wherein the first locking element is configured to lock the body portion at a first position relative to the bearing retainer when the first locking element is in the locked position and the second locking element is in the unlocked position, the first position corresponding to a first compression ratio of the engine, and the second locking element is configured to lock the body portion at a second position relative to the bearing retainer when the second locking element is in the locked position and the first locking element is in the unlocked position, the second position corresponding to a second compression ratio of the engine, and wherein the second compression ratio is larger than the first compression ratio.
2. The connecting rod assembly of
3. The connecting rod assembly of
4. The connecting rod assembly of
5. The connecting rod assembly of
6. The connecting rod assembly of
7. The connecting rod assembly of
9. The connecting rod assembly of
10. The connecting rod assembly of
11. The connecting rod assembly of
12. The connecting rod assembly of
15. The engine of
16. The engine of
17. The engine of
18. The engine of
19. The engine of
20. The engine of
22. The engine of
24. The engine of
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1. Field of the Invention
The invention relates to a variable compression connecting rod for use with an internal combustion engine.
2. Background Art
A "compression ratio" of an internal combustion engine is defined as the ratio of the volume in a cylinder above a piston when the piston is at bottom-dead-center (BDC) to the volume in the cylinder above the piston when the piston is at top-dead-center(TDC). The higher the compression ratio, the more the air and fuel molecules are mixed and compressed, thereby resulting in increased efficiency of the engine. This in turn results in improved fuel economy and a higher ratio of output energy versus input energy of the engine.
In conventional internal combustion engines, however, the compression ratio is fixed and cannot be changed to yield optimal performance. Accordingly, variable compression ratio (VCR) internal combustion engines have been developed to vary the clearance volume of a cylinder in order to achieve improved fuel economy and increased engine power performance. Such VCR engines are designed to have a higher compression ratio during low load conditions, and a lower compression ratio during high load conditions. Known techniques include using "sub-chambers" and "sub-pistons" to vary the volume of a cylinder (see, for example, U.S. Pat. Nos. 4,246,873 and 4,286,552), varying the actual dimensions of all or a portion of a piston attached to a fixed length connecting rod (see U.S. Pat. No. 5,865,092), and varying the actual length of a connecting rod (see U.S. Pat. No. 5,724,863).
Other techniques include the use of eccentric rings or bushings either at the lower "large" end of a connecting rod or the upper "small" end of the connecting rod for varying the effective length of the connecting rod or height of a reciprocating piston. U.S. Pat. Nos. 5,417,185, 5,562,068 and 5,960,750 and Japanese Publication JP-03092552 disclose devices that include eccentric rings. These eccentric ring devices, however, are undesirable in that each eccentric ring must be rotated 180 degrees before one of the desired operating modes or positions is engaged. As a result, locking of the eccentric ring in a proper position may not occur within an optimum period of time, thereby leaving the effective length of the device and consequently the compression ratio of an associated cylinder in an undesired intermediate state.
The invention addresses the shortcomings of the prior art by providing a connecting rod assembly that may be transitioned quickly and reliably between two or more compression modes without requiring rotation of an eccentric ring member about a crankpin or wrist pin.
The connecting rod assembly of the invention is configured to vary a compression ratio of an internal combustion engine having a crankshaft and a piston. The assembly includes a first portion adapted to be connected to the crankshaft and having a cylindrical aperture. The assembly further includes a second portion adapted to be connected to the piston and movable with respect to the first portion. In addition, the assembly includes a locking element having a cylindrical portion that is disposed at least partially in the cylindrical aperture. The locking element is movable between an unlocked position and a locked position for locking the second portion at a first position relative to the first portion, wherein the first position corresponds to a first compression ratio of the engine.
The engine 12 shown in
Each connecting rod assembly 32 is in fluid communication with the fluid supply system 14, and is operative to vary the compression ratio of the engine 12 as explained below in greater detail. "Compression ratio" for a particular cylinder 22 is defined as the ratio of the volume in combustion chamber 28 above the piston 30 when the piston 30 is at bottom-dead-center (BDC) to the volume in the combustion chamber 28 above the piston 30 when the piston 30 is at top-dead-center (TDC). Although each connecting rod assembly 32 is described below as providing first and second or high and low compression ratios, each connecting rod assembly 32 may be configured to provide one or more intermediate compression ratios for the engine 12.
Referring to
When both valves 44 and 46 are closed, the low pressure pump 38 may operate to provide oil at a first pressure to the engine 12 for lubrication purposes. Such oil may be provided, for example, through one or both passage arrangements 40 and 42 to main bearings 48, and/or through third passage arrangement 50 to the cylinder head (not shown) of the engine 12.
When one of the valves 44 or 46 is open, the high pressure pump 39 and/or an accumulator 51, which stores high pressure oil, may provide oil at a second pressure greater than the first pressure to one of the passage arrangements 40 or 42. This oil is then provided to the connecting rod assemblies 32 so as to cause a change in the effective length of the connecting rod assemblies 32, and thereby vary the compression ratio of the engine 12, as explained below in greater detail.
The fluid supply system 14 may further include check valves 52 for isolating the low pressure pump 38 from high pressure oil. The check valves 52 may be disposed in connector passage 53 that extends between the passage arrangements 40 and 42.
The fluid supply system 14 and connecting rod assemblies 32 may be operated to effect a change in the compression ratio of the engine 12 in accordance with one or more operating parameters, such as engine load and speed. Referring to
Returning to
The bearing retainer 69 is configured to retain a bearing 71 between the bearing retainer 69 and the crankpin 34, and includes a bearing retainer axis 72 that is coincident with crankpin axis 73. The bearing retainer 69 may further include first and second sections 74 and 75, respectively, that are joined together in any suitable manner, such as with bolts, screws or other suitable fasteners (not shown). In addition, the bearing retainer 69 includes first and second continuous, circumferential grooves or channels 76 and 77 that receive fluid from fluid supply system 14.
The bearing retainer 69 also includes one or more apertures disposed proximate each end of the bearing retainer 69. Referring to
Similarly, the second section 75 defines a second end 88 of the bearing retainer 69, and includes third and fourth cylindrical apertures or bores 90 and 92, respectively, disposed proximate the second end 88. The second section 75 further includes third and fourth extension apertures 94 and 96, respectively, extending from the third and fourth cylindrical bores 90 and 92, respectively. The extension apertures 94 and 96 may have any suitable configuration, such as described above with respect to the extension apertures 84 and 86.
Returning to
Furthermore, the body portion 70 is axially movable with respect to the bearing retainer 69 between a first position, or unextended position shown in
The connecting rod assembly 32 also includes first and second locking mechanisms 108 and 110, respectively, for locking the body portion 70 at the unextended and extended positions. Each locking mechanism 108 and 110 includes one or more locking elements 112 that are each moveable laterally between an unlocked position and a locked position. Referring to
Referring to
Referring to
Similarly, when the locking elements 112 of the second locking mechanism 110 are in the locked positions, each first fluid passage 122 of the second locking mechanism 110 is substantially aligned with a second unlocking fluid passage 127 that extends between a respective cylindrical bore 90 or 92 and the first channel 76. When the locking elements 112 of the second locking mechanism 110 are in the unlocked positions, each second fluid passage 124 of the second locking mechanism 110 is substantially aligned with a second locking fluid passage 128 that extends between a respective cylindrical bore 90 or 92 and the second channel 77.
The fluid passages 122 and 124 may have any suitable configuration for receiving fluid from the fluid supply system 14, as explained below in greater detail. In the embodiment shown in
Still referring to
While each locking projection 115 may have any suitable configuration, such as a cylindrical projection or a rectangular projection, in the embodiment shown in
Each locking mechanism 108 and 110 may further include one or more springs 140 and one or more cover plates 142 that are attachable to the bearing retainer 69. Each spring 140 is disposed between and engaged with a respective locking element 112 and a respective cover plate 142. Furthermore, each spring 140 is configured to urge a respective locking element 112 toward the locked position. In the embodiment shown in
Referring to
Referring to
More specifically, referring to
With both locking mechanisms 108 and 110 in the unlocked position, the body portion 70 is able to move axially relative to the bearing retainer 69 from the extended position shown in
When the engine controller 16 determines that it is desirable to change back to high compression mode, the engine controller 16 may control operation of the fluid supply system 14 so as to route pressurized oil through the second passage arrangement 42. Next, pressurized oil may travel through second crankshaft passage arrangement 146 and second bearing aperture or apertures (not shown) in bearing 71, and then into second channel 77 of bearing retainer 69. Pressurized oil passing from second channel 77, through first unlocking fluid passages 125, then acts on the first locking mechanism 108 so as to move the associated locking elements 112 to the unlocked position, thereby allowing the body portion 70 to move from the unextended position shown in
The connecting rod assembly 32 of the invention includes several beneficial aspects. First, as shown in the
Further, each locking element 112 is compressively loaded, rather than shear loaded, between the bearing retainer 69 and the body portion 70 when the locking element 112 is in the locked position. Such compressive loading reduces the possibility of bending the locking elements 112.
In addition, because the cylindrical portions 114 of the locking elements 112 mate with the cylindrical bores 80, 82, 90 and 92, the locking elements 112 may exhibit smooth lateral movement. In other words, the cylindrical bores 80, 82, 90 and 92 may act as guides for controlling lateral movement of the locking elements 112.
Furthermore, because the connecting rod assembly 32 may be manufactured with close tolerances between the cylindrical portions 114 and the cylindrical bores 80, 82, 90 and 92, fluid leakage around the cylindrical portions 114 may be minimized. Similarly, because the locking projections 115 closely mate with the extension apertures 84, 86, 94 and 96, fluid leakage from the cylindrical bores 80, 82, 90 and 92 may be minimized.
While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.
Rao, V. Durga Nageswar, Imai, Yash Andrew, Sashidharan, Pravin, Styron, Joshua Putman
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Nov 12 2001 | SASHIDHARAN, PRAVIN | Ford Motor Company | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 012355 | /0785 | |
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